pub fn expected_minutes_in_oven() -> i32 {
    const EXPECTED_TIME: i32 = 40;
    EXPECTED_TIME
}

pub fn remaining_minutes_in_oven(actual_minutes_in_oven: i32) -> i32 {
    expected_minutes_in_oven() - actual_minutes_in_oven
}

pub fn preparation_time_in_minutes(number_of_layers: i32) -> i32 {
    const TIME_REQUIRED_FOR_A_LAYER: i32 = 2;
    number_of_layers * TIME_REQUIRED_FOR_A_LAYER
}

pub fn elapsed_time_in_minutes(number_of_layers: i32,
                               actual_minutes_in_oven: i32) -> i32 {
    preparation_time_in_minutes(number_of_layers) + actual_minutes_in_oven
}