Macroeconomics Tax Problem ~ Help Please? ~

The equilibrium wage is $10.00 per hour, and the equilibrium number of research assistants is 250. Suppose the government has decided to institute a$4.00 per-hour payroll on research assistants and is trying to determine the optimal way to do so. Some people argue that the employer should pay the entire tax. Others say that the tax should fall on workers. Still, others say that the fairest way to institute a the tax is to have the employer and the work each pay half the tax.

Here is the chart I have to fill out. I took a screenshot of it.. I honestly have no clue where to start.

They also provided a graph of the equilibrium wage and number of assistants: