Grace works from 10 to 20 hours per week while attending college. she earns $9.00 per hour. her roommate frances, also has a job. her pay for t hours each week is given by the function f(t)=10t, where 5 is less than or equal to t which is less than or equal to 15. compare their hourly wages and the amount they each earn per week.

18

step-by-step explanation:

there is only one way to arrange all the eight relative to each other because they are not distinct. we have

now there are nine places to place an (and not more than one in one place).   because we have four symbols, we need to choose four of these nine places to insert an . order does not matter because the are not distinct.

thus there are 1 · c(9,4) ways, or, if we calculate it,

thus there are 126 ways to form such "words."