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# helpme

what should go to in the part where it isdeclaring 2 dimension array? I get compiler error

Math.cs
```using System;
namespace Treehouse.CodeChallenges
{
public static class MathHelpers
{
public static int[][] BuildMultiplicationTable(int maxFactor)
{
Array[][] array = new Array[maxFactor][];
for(int i=0; i<=maxFactor; i++)
{
for(int j=0; j<=maxFactor; j++)
{
array[i][j] = i*j;
}
}
}
}
}
```

Here's a few hints:

• the array size must be larger than the highest index used
• each row must be separately initialized
• the function must return the completed table
```namespace Treehouse.CodeChallenges
{
public static class MathHelpers
{
public static int[][] BuildMultiplicationTable(int maxFactor)
{
int[][] sheet = new int[maxFactor+1][];

for(int i=0; i<=maxFactor; i++)
{
for(int j=0; j<=maxFactor; j++)
{
sheet[i][j] = i*j;

}
}
return sheet;
}
}
}
```

how about this i got error "Object reference not set to an instance of an object"

It looks like you implemented 2 of my 3 hints, but you still need to initialize each row by creating an array for the 2nd dimension.

You might want to take another look at the Jagged Arrays video, particularly around 4:40 where the rows are created.