Dave is buying popcorn and sodas for his son and his three friends(4 kids total). He needs to buy atpeast one of the two items for each of the four. Popcorn costs $2.50 per bag and sodas cost $4.00 each. Dave can spend at most $20.00 if s represents the number of sodas and p represents the number of bags of popcorn, then write a system that models this scenario