Ruben, age $16$ and single, is claimed as a dependent by his father and mother. During $2023,$ Ruben received cash dividends totaling $$3,200,$ and interest totaling $$1,200.$ Ruben also received $$700$ working at a summer job. Answer the questions below and show your computations using good form.

a$.$ How much is Ruben's taxable income for $2023?$

b$.$ Suppose Ruben received $$13,900($not $$700)$ from the summer job. Now, how much is Ruben's taxable income for $2023?$

c$.$ Suppose that Ruben is both deaf and blind and that he received $$1,100($not $$700)$ from the summer job. Now, how much is Ruben's taxable income for $2023?$