Python calculating letter grades

score1=float(input("Enter score 1: "))

score2=float(input("Enter score 2: "))

score3=float(input("Enter score 3: "))

score4=float(input("Enter score 4: "))

score5=float(input("Enter score 5: "))

calc_average= sum(scores)/len(scores)

scores=[score1,score2,score3,score4,score5,calc_average]

def determine_grade(scores):

    if score >=90:
        return 'A'
    elif score >=80:
        return 'B'
    elif score >=70:
        return "C"
    elif score >=60:
        return "D"
    elif score <60:
        return "F"
determine_grade(scores)

print("scores \t numeric grade \t letter grade")

print("-------------------------------------------------------------")

print("Score 1: ","\t", score1,"\t", determine_grade(score1))

print("Score 2: ","\t", score2,"\t", determine_grade(score2))

print("Score 3: ","\t", score3,"\t", determine_grade(score3))

print("Score 4: ","\t", score4,"\t", determine_grade(score4))

print("Score 5: ","\t", score5,"\t", determine_grade(score5))

print("-------------------------------------------------------------")

calc_average= sum(scores)/len(scores)

avgLetter= determine_grade(calc_average)

print("Average Score: {0:.2f}".format(calc_average),"\t",avgLetter)

When I plug this in the letter grade returns F for all inputs and I'm unsure why