Separable Equations please help

I've been trying to solve this problem for quite a while now but can't seem to get the right answer. please any pointer will be greatly appreciated.

A tank contains 50 kg of salt and 1000 L of water. A solution of a concentration 0.025 kg of salt per liter enters a tank at the rate 7 L/min. The solution is mixed and drains from the tank at the same rate.

Find the amount of salt in the tank after 2.5 hours.

Find the concentration of salt in the solution in the tank as time approaches infinity.

my dy/dt equation looks like this dy/dt = .175-7y/1000

after doing the steps my book shows I end up with a really long equation that doesn't help at all.

I know that y(0)=80 kg has to help me find c but the answer is totally wrong. I don't know where did I messed up. Please help.