Practice: Functions and Conditionals

For each problem, write the function with examples (including boundary cases) first, then the body.

1. sale-price : Number, Number → Number

Given an item's price and a discount percentage, return the price after the discount, then add 7% sales tax.

sale-price(100, 20) → 85.6

2. initials : String, String → String

Given a first and last name, return the two initials in uppercase.

initials("grace", "Hopper") → "GH"

3. parking-fee : Number → Number

Given whole hours parked, return the fee. The first hour is free, hours 2 through 4 cost $3 per hour, and any time over 4 hours costs a flat $20 for the day.

parking-fee(1) → 0
parking-fee(3) → 6
parking-fee(6) → 20

4. can-ride : Number, Number, Boolean → Boolean

Given a height in inches, an age, and whether an adult is along, return whether someone may ride. They must be at least 48 inches tall, and either be at least 10 years old or have an adult along.

can-ride(50, 8, true) → true
can-ride(50, 8, false) → false
can-ride(40, 12, false) → false