A system employs paging and segmentation both. Each virtual address $($s$,$ p$,$ w$)$ requires three memory accesses except the TLB access time. To speed up the address translation, a translation look$-$aside buffer $($TLB$)$ holds the component $($s$,$ p$)$ together with the corresponding frame number. If each memory access takes m ns and the access to TLB takes m$/10$ ns$,$ determine the hit ratio h necessary to reduce the average access time to memory $($three memory access$)$ by $20\%.$