If $$t_c$$, h and $$t_m$$ specify the cache access time, hit ratio and main memory access time then the average access time is (given $$t_c = 160 ns, t_m = 960 ns, h = 0.90$$)

A

160 ns

B

960 ns

C

256 ns

D

960 $$\times$$ 0.9 ns