In Exercises 43-54, write the argument using propositional wffs (use the statement letters shown). Then, using propositional logic, including the rules in Table 1.14, prove that the argument is valid. 43. If the program is efficient, it executes quickly. Either the program is efficient, or it has a bug. However, the 46. The crop is good, but there is not enough water. If there is a lot of rain or not a lot of sun, then thereis 52. If the birds are flying south and the leaves are turning, then it must be fall. Fall brings cold weather. The 56. The argument of the defense attorney at the beginning of this chapter was program does not execute quickly. Therefore, it has a bug. E, Q, B enough water. Therefore, the crop is good and there is a lot of sun. C, w,R, s leaves are turning but the weather is not cold. Therefore, the birds are not flying south. B, L, F, C