Problem $1(20$ points$).$ Consider the following regular expressions $($we omit the dot operator$)$

R$0=1|2|3|4|5|6|7|8|9$

R$1=0|1|2|3|4|5|6|7|8|9$

R$2=(0|1)*$ R$0(0|1)$

R$3=00$ R $0*(0|1)*$

R$4=$ R$3*$ R$2*000$