If a mammal gives birth to live animals, how is a monotreme a mammal if it lays eggs? This has been confusing me for the past like hour

In some ways, monotremes are very primitive for mammals because, like reptiles and birds, they lay eggs rather than having live birth. ... Like other mammals, however, monotremes have a single bone in their lower jaw, three middle ear bones, high metabolic rates, hair, and they produce milk to nourish the young.

Explanation:

it also supports my hypothesis. if you rest first you can squeeze the clothespin more times. from the data i collected the average of the eight people concluded exercise makes your muscles more fatigued and less able to squeeze the clothespin compared to resting before squeezing.