ACT Problem 20

$$\begin{array}{lcl} 20.\:The\:average\:of\:a\:set\:of\:7\:positive\:integers\:is\:22.\:When\\ a\:eighth\:number\:is\:included,\:the\:average\:of\:the\:the\:set\\ increases\:to\:28.\:What\:is\:the\:eighth\:number?\\ \\ \\ (A):89\\ (B):70\\ (C):54\\ (D):75\\ (E):36\\ \end{array}$$