2. (12.5 points) {={a,b,c}, L={s: s starts with a, ends with c, and #.(s) = (n2+n)/2,n21}. For example, s=abbcbbabbc e L, because s starts with a, ends with C, #(s) = 6 = (32+3)/2; s=abbcbbabb & L because s does not end with c; and s=abcbbabbc & L because #(s) = 5, and 5 + (n2+n)/2 for any n 2 1. Prove that L CFLs using the CF pumping theorem. Feel free to use the fact the CFLs closed under intersection with the RLS