sleep debt calculator

function getSleepHours(day){
if (day === "monday"){
return 8;
} else if (day === "tuesday"){
return 8;
} else if (day === "wednesday"){
return 8;
} else if (day === "thursday"){
return 8;
} else if (day === "friday"){
return 8;
} else if (day === "saturday"){
return 8;
} else if (day === "sunday"){
return 8;
}
}
getSleepHours("Monday")
I am wondering why the hours will not show on preview?