(2) (10 points) A monotone SAT formula is a SAT formula with no negated variables. So, for example, $ = (21 V x2 Vx3) A (X2 V 23 V X4) A (21 V X4) is a monotone formula. A monotone formula is easy to satisfy, we can simply set all variables to be true. In the MONOTONE SAT problem we are given a monotone formula and an integer k, and ask if there is a way to satisfy formula & with setting at most k variables true (and the rest of the variables false). Show that the MONOTONE SAT problem is NP-complete