Isaac makes china mugs with names painted on them. He charges a fixed fee for the mug, together with a fixed charge for each letter in the name. Penelope buys a mug for each of her children, Alexander and Lucia. She pays $12.60 for Alexander’s mug and $9.40 for Lucia’s mug. How much would Penelope have to pay for a mug with her own name on it?

Not completely sure, and I know its late but for the other people that look at this, 11.80$

Step-by-step explanation:

I found how many more letters Alexander had over Lucia, then when I got 4 divided it in-between 12.60 - 9.40 (3.20)  I got 0.8. knowing the letter cost i got the initial fee for the mug (5.40) and added 8x0.8 to it, resulting in my answer 11.80$