Mr$.$ and Mrs$.$ K file a joint income tax return. Compute their standard deduction

assuming that:

a$)$ Mr$.$ K is age $68$ and Mrs$.$ K is age $60.$

b$)$ Mr$.$ K is age $70$ and Mrs$.$ K is age $68.$

c$)$ Mr$.K$ is age $70$ and Mrs$.K$ is age $68.Mrs.K$ is legally blind.