4) For the combinational circuit shown below A B D- T3 DF F T4 F2 a. Write the Boolean expressions of T1 through 74. Write also the Boolean functions F1 and F2 in terms of the four input variables. b. Obtain the truth table showing the binary values of 71 through 74 and the output functions F1 and F2 for all combinations of the four inputs (A, B, C, and D). c. Simplify the functions F1 and F2 by using the Karnaugh map method.