def calculate_expected_offspring(numbers, offspring=2):
    """
Given a list of six positive integers and the number of offspring per pair (default=2),
calculate the expected number of offspring with a dominant allele.
    """
    dominant_offspring_likelihood = {
        1: 1 * offspring,
        2: 1 * offspring,
        3: 1 * offspring,
        4: 0.75 * offspring,
        5: 0.5 * offspring,
        6: 0 * offspring
    }
    
    #For each position in the list of 6 numbers (index 0-5),
    # multiply the number of pairs by the chance of producing
    # offspring with a dominant phenotype given the number
    # of offspring each pair produces.
    dominant_offspring = (
    numbers[0] * dominant_offspring_likelihood[1] +
    numbers[1] * dominant_offspring_likelihood[2] +
    numbers[2] * dominant_offspring_likelihood[3] +
    numbers[3] * dominant_offspring_likelihood[4] +
    numbers[4] * dominant_offspring_likelihood[5] +
    numbers[5] * dominant_offspring_likelihood[6])
    
    return(dominant_offspring)