She conducted 36 tastings.
10 tastings are in the category of the first 10 tastings.
10 * $1.50 = $15.00
36 - 10 = 26
Out of the remaining 26 tastings, 20 are int eh category of "the next 20 tastings."
20 * $2.50 = $50.00
This accounts for 10 + 20 = 30 tastings.
36 - 30 = 6
She did 6 tastings beyond the 30 tastings, so for the last 6 tastings, she gets paid
6 * $4.00 = $24.00
The total pay is:
$15.00 + $50.00 + $24.00 = $89.00