Answer:
Total tiles need - 30 large tiles and 0 small tiles
Minimum cost is $135
Explanation:
Allow dimensions are

Smallest allowed dimensions are
2 things need to be noticed
1. smaller thee total size of final mosaic, cheaper the cost
2. Greater thee number of large tiles, cheaper the mosaic
Place
to fully cover the size of rectangle
and

.
Therefore,total tiles need
(& 0 small tiles).
The minimal cost is
