239.

m = 250, k = 4. m * k = 250 * 4 = 1000.

m = 340, k = 2. m * k = 340 * 2 = 680.

m = ?, k = 20. m * k = 1000. m = 1000 / 20 = 50.

m = ?, k = 90. m * k = 720. m = 720 / 90 = 8.