After Retirement, Kelly's Company Offers Her Two Options for Receiving $\$ 700$

After retirement, Kelly's company offers her two options for receiving her retirement pension. According the the first plan, she will receive monthly payments from a variable annuity that initially pays $\$ 700$ per month then decreases each month at a rate of $\$ 25$ per month per year. Optionally, she may choose a plan that pays her a fixed amount of $\$ 500$ per month for the rest of her life. The monthly payments for the two plans are illustrated in the graph below. After how many years does the variable plan pay less per month than the fixed plan?

A) Up to 8 years
B) 8 years
C) 9 years
D) The variable plan always pays less.