What is the last digit of the expression below?  $$\underbrace{4\times4\times4\times\cdots\times4}_{100} \times \underbrace{7\times7\times7\times\cdots\times7}_{100} \times \underbrace{9\times9\times9\times\cdots\times9}_{100} \times \underbrace{11\times11\times11\times\cdots\times11}_{100}$$ 
Overseas Competition->Knowledge Point->Calculation Modules->Whole Numbers->Calculation of Multi-digit Numbers