Layla decides to start a business making fun-patterned masks for people to wear in public. On her first trip to the fabric store, Layla buys 4 yards of fabric and enough elastic to make ear loops for $21.32. She quickly realizes that her family and friends have started telling others about her business and she gets more orders than expected. So, Layla goes back to the store in a rush and gets 7 yards of fabric and more elastic for $30.38.

a. Write a linear equation that models the cost of the materials, C, in terms of the number of yards purchased, n.

b. If Layla has a monthly budget of $150 to purchase fabric, how many whole yards of fabric (and the necessary elastic) can she purchase in a month? Be sure to round down so she doesn't go over her budget.