Explanation:
8x + 4y <= 136
2x + y <= 34
trying (15, 9) :
2x + 7y <= 70
2×15 + 7×9 <= 70
30 + 63 <= 70
93 <= 70
that does not work. so, (15, 9) is not a valid point of f(x, y) and therefore also no maximum.
trying (0, 10) :
2×0 + 7×10 <= 70
70 <= 70
that is true.
2×0 + 10 <= 34
10 <= 34
also true.
so, (0, 10) is the correct answer option.