help in question 10, 12 and 14

6. Biochemists use cutting sequences to analyse DNA by cutting the DNA sequence at specific points. Some cutting sequences have length six. For ex- ample, AAGCTT is a cutting sequence. Cutting se- quences are usually not palindromic, but they have a palindromic property. If we read the sequence in reverse order, and exchange T and A and also ex- change G and C, the sequence is unaltered. Notice that the sequence AAGCTT has this property. How many sequences of length six in the letters T, A, G, C have this property