The first 10 pounds is $2 per pound so $2 x 10 = $20
She wants to pick 40 pounds so after the first 10 pounds she needs 40-10 = 30 more pounds.
The cost for those are $1 per pound so 30 x $1 = $30
Total cost = $20 + $30 = $50 for 40 pounds.
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