Discrete

Problem 1 (15 points) Model the statements below using appropriate connectives and answer the questions by identifying the rules of inference you used: [10 points] Use rules of inference to find if the following arguments are valid. Specify the rules you used in each step. If the argument is not valid, show an assignment of true/false values for which the conclusion is false 4-(r-s) t-r 9-r .[5 points] Consider the following statements: "If the posters were not printed or the catering service did not arrive on time, the award ceremony would have been cancelled and the professor would have been angry." "If the ceremony were cancelled, then apology letters would have to be sent." No apology letters were sent." Model these statements using propositions and use rules of inference to find appropriate conclusions