a) For what value of k is the graph of kx - 7y + 10 = 0 parallel to line m?

My work:

. . .slope:

. . . . .-A/B = -8/-12 = 8/12 = 4/7

. . . . .-A/B = -?/-7

. . . . .k = 4

b) What is k if the graphs of m and kx - 7y + 10 = 0 are perpendicular?

I don't know how to do this part.

The answer to part b is -49/4, but I have no idea how to get the answer. I thought all you had to do was find the opposite reciprocal but it turns out to be -7/4 NOT -49/4

Please help! Thank you!