He wants to serve 5 shrimp per guest and will have 40 guests so he needs 5*40 = <<5*40=200>>200 shrimp
Each pound of shrimp has 20 shrimp and he needs 200 shrimp so he needs 200/20 = <<200/20=10>>10 pounds of shrimp
The shrimp is $17.00 per pound and he needs 10 pounds so he will spend 17*10 = $<<17*10=170.00>>170.00 on shrimp
#### 170