The substance x and y had retention times of 16.4 and 17.63 minutes on a 30 cm column. unretained species had 1.30 minutes retention time. the peak widths (wi) were 1.11 and 1.21 min, respectively. calculate column resolution, average number of plates, and plate height.

Column Resolution
Rs = 2[(tr)y - (tr)x]/[Wx + Wy]
= 2[17.63 - 16.4]/ [1.11 + 1.21] = 1.06

Average no. of plates in the column for substance x 
N = 16(tr/ W)^2
N = 16(16.4/1.11)^2
N = 3490 plates 

Average no. of plates in the column for substance y 
N = 16(tr/ W)^2
N = 16(17.63/1.21)^2
N = 3397 plates 

Plates Height
H = L/N

For substance x 
H = 30/3490
H= 0.00916905 cm/plate 

For substance y 
H = 30/3397
H = 0.00883132 cm/plate 

So confused right here i need it to be more clearer