# Solve using different methods

for i in range$(1,$ len$($t$))$:

rho $=$ reactivity$($t$[$i $-1])$

# Explicit Euler

N$\_$explicit$[$i$],\_=$ explicit$\_$euler$\_$step$($N$\_$explicit$[$i $-1],$ C$\_$ref$[$i $-1],$ At$)$

# Modified Euler

N$\_$modified$[$i$],\_=$ modified$\_$euler$\_$step$($N$\_$modified$[$i $-1],$ C$\_$ref$[$i $-1],$ At$)$

# $4$th Order Runge$-$Kutta

N$\_$rk$[$i$],\_=$ runge$\_$kutta

I think this part of code is not finished till the end or not needed?