13. Mariya has purchased a new smart phone and is trying to decide on a service plan. Without a plan each minute of use costs 0.30 and each megabyte of data costs 0.05 A plan that allows unlimited talk and data costs 100/month . Under which circumstances is the plan a better choice for Mariya?

Let 'm' represent the number of minutes Mariya uses per month and 'd' represent the number of megabytes of data she uses per month.The cost without a plan is calculated as: 0.30m + 0.05dThe cost with the plan is a fixed 100 on data alone.* **High Minute Usage:** If Mariya uses 500 minutes per month, the inequality becomes: 0.30 * 500 + 0.05d > 100 => 150 + 0.05d > 100. Again, the plan is *always* better regardless of her data usage, as she'd already be spending more than 110. The plan is a better choice in this scenario.**In conclusion:** The plan is a better choice for Mariya if her combined usage of minutes and data results in a cost greater than $100 per month according to the formula 0.30m + 0.05d. High usage of either minutes or data individually can quickly make the plan the more economical option.