A direct mapped cache has a hit rate of $95\%,$ a hit time of $4$ ns$,$ and a miss penalty of $100$ ns$.$ An L$2$ cache is a dded with a hit time of $20$ns and a hit rate of $50\%,$ what is the new AMAT?Select one:a$.$ noneb. $7$ nsc$.7\mathrm{.}5$ nsd$.8$ nse. $8\mathrm{.}5$ ns