perform addition in Sheet1 cells and store the result in Sheet2 cell

Hi expert,

I need a formula to add values from
B1, D1, G1, I1, K1 ,B2, D2, G2, I2, K2 ,B3, D3, G3, I3,, K3 cells from sheet1. (if this cell has null add Defalut Zero and here D2 has null so while adding consider this cell by assuming it has value Zero ) and store the final result in sheet2 B2 cell .

Please give a formula

Thanks,
sample data.xlssample data.xls