If-and-then function in FormCalc

Dear friends,

Please be so kind to assist. I am creating a form in LiveCycle and need to insert a formula in a field

Basically I need that if the value in DropDownList2 is Great Park and in DropDownList3 is Big Water then the value in NumberField1 should be 250.

Could anyone be so kind to provide me a script in FormClac?

Thanks! Cheers!