The relationship between a person's age and the monthly cost to cover that person with a certain life insurance policy can be modeled by the equation y=0.5x+10 , where x is the person's age and y is the monthly cost in dollars. Which of these statements is true according to the model?
a. It costs $40 a month to cover a 30-year-old
b. It costs $40 a month to cover a 20-year-old
c. It costs $30 a month to cover a 40-year-old
d. It costs $20 a month to cover a 40-year-old
