Ash and Bea are engravers. Ash charges a flat fee of $\$1.50$ for the first $21$ letters engraved, and $8$ cents per letter thereafter. Bea charges a flat fee of $\$1.60$ for the first $15$ letters engraved, and $7$ cents per letter thereafter. For what nonzero number of letters will Ash and Bea's engraving prices be the same?
