Machine oil is blended by mixing $300$ kg$/$min of No$.25$ oil with $100$ kg$/$min of No$.50$ oil in a tank.The oil is well mixed and is withdrawn at the rate of $380$ kg$/$min$.$ Assume the tank contains no oil at the start of the blending process.

a$)$ Firstly, classify the process $($Is it a continuous, a batch or a semi batch process?$).$ Secondly again classify the process $($Is it a steady$-$state or a transient process?$).$

b$)$ Write a mass balance for the process. Identify the terms of the general balance equation present in your equation and state the reason for omitting any terms

c$)$ How much oil is in the tank after one hour?