$11$ Ricky earns $$84365$ as a cabaret artist and $$4620$ from his share portfolio. He has tax deductions of $$13884$ and, throughout the year, pays a total of $$15988$ in tax instalments.

a Find his taxable income.

b Calculate the Medicare levy Ricky needs to pay.

c Find the income tax payable on his taxable income.

d Find the tax refund or tax balance. payable.