The cost function for $q$ units of a certain item is $C(q)=97q+102.$ The revenue function for the same item is $R(q)=97q+\frac{49q}{lnq}$

a$.$ Find the marginal cost.

b$.$ Find the profit function.

c$.$ Find the profit from one more unit sold when $8$ units are sold.

a$.$ The marginal cost is