A tank contains 70 kg of salt and 1000 L of water. Pure water enters a tank at the rate 10 L/min. The solution is mixed and drains from the tank at the rate 5 L/min. (a) What is the amount of salt in the tank initially? amount = (kg) (b) Find the amount of salt in the tank after 3 hours. amount = (kg) (c) Find the concentration of salt in the solution in the tank as time approaches infinity. (Assume your tank is large enough to hold all the solution.) concentration = (kg/L) (1 point) Use the "mixed partials" check to see it the following differential equation is exact. If it is exact find a function F(x,y) whose differential, dF(x, y) is the left hand side of the differential equation. That is, level curves F(x, y) = C are solutions to the differential equation: (3xy² − 2y)dx + (3x² y − 2x)dy = 0 First: My(x, y) = 6xy-2 and Nx(x, y) = 6xy-2 If the equation is not exact, enter not exact, otherwise enter in F(x, y) here 3x^2y^2+2xV