Formation of , heat, , or a can be the result of a chemical change.

The expression that represents the estimated cost for the party is T=s×i

Step-by-step explanation:

1) We can get an estimated cost for the party by using the following expression:

T=s×i

where:

T: total cost of the ice cream party ($)

s: number of ninth students (person)

i: unit cost of ice cream ($/person)

2) If we choose the letter "s", it can take whole number values.

For example: s={1,2,3,4,5,...,25}

If we choose the letter "i", it can take rational values (sometimes the price of the items are not expresed as a whole number).

For example: s={1.25,2.50,3.00,4.75,5.00}