Phone plan a advertises a rate of $0.25 per minute, while phone plan b advertises a rate of $0.17 per minute for the first 100 minutes and $0.32 for each additional minute. • identify which plan has a variable rate of change and explain why the rate is variable. • identify the cost for phone plan a and for phone plan b when 100 minutes are used. show all your work. • compare plan a and plan b and describe when phone plan a is a better deal than plan b