3. (15 points) A function is defined as below: F(a,b,c,d)= m(0,3,5,7,8,9,10,12,13)+ d(1,6,11,14). 1) Find all essential prime implicants. 2) Find two minimum sum-of-products expressions out of three ones. 3) In your minimum expressions, which don't care's are considered as '1'?