Consider a Boolean function f(a,b,c,d) (4 binary inputs: a,b,c,d, and 1 output) that outputs the value 1 if and only if the number of 1 's in a and b is less than or equal to the number of 1 's in c and d.
(a) Write a truth table for function f.
(b) Construct K-map for function f, and write the minimal expression for function f in the sum-of-product (SOP) and product-of-sum (POS) forms. Clearly show all the groupings.