I am struggling to understand how to do this problem. Please show all calculations and formulas so I can follow along.

A project manager has compiled a list of major activities that will be required to install a computer information system in her firm. The list includes estimated completion times for activities and precedence relationships. Use Table B1 and Table B2. If the project is finished within 26 weeks of its start, the project manager will receive a bonus of $1,000; and if the project is finished within 27 weeks of its start, the bonus will be $500. Find the probability of each bonus. (Round path means and path standard deviations to 2 decimal places. Round probabilities to 4 decimal places. Do not round any other intermediate calculations.) \begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|} \hlinez & .00 & .01 & .02 & .03 & .04 & .05 & .06 & .07 & .08 & .09 \\ \hline .0 & .5000 & .5040 & .5080 & .5120 & .5160 & .5199 & .5239 & .5279 & .5319 & .5359 \\ \hline .1 & .5398 & .5438 & .5478 & .5517 & .5557 & .5596 & .5636 & .5675 & .5714 & .5753 \\ \hline .2 & .5793 & .5832 & .5871 & .5910 & .5948 & .5987 & .6026 & .6064 & .6103 & .6141 \\ \hline .3 & .6179 & .6217 & .6255 & .6293 & .6331 & .6368 & .6406 & .6443 & .6480 & .6517 \\ \hline .4 & .6554 & .6591 & .6628 & .6664 & .6700 & .6736 & .6772 & .6808 & .6844 & .6879 \\ \hline .5 & .6915 & .6950 & .6985 & .7019 & .7054 & .7088 & .7123 & .7157 & .7190 & .7224 \\ \hline .6 & .7257 & .7291 & .7324 & .7357 & .7389 & .7422 & .7454 & .7486 & .7517 & .7549 \\ \hline .7 & .7580 & .7611 & .7642 & .7673 & .7703 & .7734 & .7764 & .7794 & .7823 & .7852 \\ \hline .8 & .7881 & .7910 & .7939 & .7967 & .7995 & .8023 & .8051 & .8078 & .8106 & .8133 \\ \hline .9 & .8159 & .8186 & .8212 & .8238 & .8264 & .8289 & .8315 & .8340 & .8365 & .8389 \\ \hline 1.0 & .8413 & .8438 & .8461 & .8485 & .8508 & .8531 & .8554 & .8577 & .8599 & .8621 \\ \hline 1.1 & .8643 & .8665 & .8686 & .8708 & .8729 & .8749 & .8770 & .8790 & .8810 & .8830 \\ \hline 1.2 & .8849 & .8869 & .8888 & .8907 & .8925 & .8944 & .8962 & .8980 & .8997 & .9015 \\ \hline 1.3 & .9032 & .9049 & .9066 & .9082 & .9099 & .9115 & .9131 & .9147 & .9162 & 9177 \\ \hline 1.4 & .9192 & .9207 & .9222 & .9236 & .9251 & .9265 & .9279 & .9292 & .9306 & .9319 \\ \hline 1.5 & .9332 & .9345 & .9357 & .9370 & .9382 & .9394 & .9406 & .9418 & .9429 & .9441 \\ \hline 1.6 & .9452 & .9463 & .9474 & .9484 & .9495 & .9505 & .9515 & .9525 & .9535 & .9545 \\ \hline 1.7 & .9554 & .9564 & .9573 & .9582 & .9591 & .9599 & .9608 & .9616 & .9625 & .9633 \\ \hline 1.8 & .9641 & .9649 & .9656 & .9664 & .9671 & .9678 & .9686 & .9693 & .9699 & .9706 \\ \hline 1.9 & .9713 & .9719 & .9726 & .9732 & .9738 & .9744 & .9750 & .9756 & .9761 & .9767 \\ \hline 2.0 & .9772 & .9778 & .9783 & .9788 & .9793 & .9798 & .9803 & .9808 & .9812 & .9817 \\ \hline 2.1 & .9821 & .9826 & .9830 & .9834 & .9838 & .9842 & .9846 & .9850 & .9854 & .9857 \\ \hline 2.2 & .9861 & .9864 & .9868 & .9871 & .9875 & .9878 & .9881 & .9884 & .9887 & .9890 \\ \hline 2.3 & .9893 & .9896 & .9898 & .9901 & .9904 & .9906 & .9909 & .9911 & .9913 & .9916 \\ \hline 2.4 & .9918 & .9920 & .9922 & .9925 & .9927 & .9929 & .9931 & .9932 & .9934 & .9936 \\ \hline 2.5 & .9938 & .9940 & .9941 & .9943 & .9945 & .9946 & .9948 & .9949 & .9951 & .9952 \\ \hline 2.6 & .9953 & .9955 & .9956 & .9957 & .9959 & .9960 & .9961 & .9962 & .9963 & .9964 \\ \hline 2.7 & .9965 & .9966 & .9967 & .9968 & .9969 & .9970 & .9971 & .9972 & .9973 & .9974 \\ \hline 2.8 & .9974 & .9975 & .9976 & .9977 & .9977 & .9978 & .9979 & .9979 & .9980 & .9981 \\ \hline 2.9 & .9981 & .9982 & .9982 & .9983 & .9984 & .9984 & .9985 & .9985 & .9986 & .9986 \\ \hline 3.0 & .9987 & .9987 & .9987 & .9988 & .9988 & .9989 & .9989 & .9989 & .9990 & .9990 \\ \hline 3.1 & .9990 & .9991 & .9991 & .9991 & .9992 & .9992 & .9992 & .9992 & .9993 & .9993 \\ \hline 3.2 & .9993 & .9993 & .9994 & .9994 & .9994 & .9994 & .9994 & .9995 & .9995 & .9995 \\ \hline 3.3 & .9995 & .9995 & .9995 & .9996 & .9996 & .9996 & .9996 & .9996 & .9996 & .9997 \\ \hline 3.4 & .9997 & .9997 & .9997 & .9997 & .9997 & .9997 & .9997 & .9997 & .9997 & .9998 \\ \hline \end{tabular} 1. Areas under the standardized nomal curve, from to z