This is a question on opportunity cost. I had problem in solving the last part. Please help me out.
Consider this allocation:
Apple: $55$ hours on Phones, $15$ hours on Tablets.
Samsung: All $70$ hours on Tablets.
I leave it as an excercise for you to check it works.
Initially what I thought was having each company produce what they're most efficient in, then change it and have Apple produce one Tablet more until it worked, as initially the Tablets were falling short.