Calculating Minimum Width for 5 Interference Maxima

[msk172]

Homework Statement

Ramon has a coherent light source with wavelength 554 nm. He wishes to send light through a double slit with slit separation of 1.5 mm to a screen 90 cm away. What is the minimum width of the screen if Ramon wants to display five interference maxima?

Homework Equations

λ/s = w/D

λ= wavelength (554nm - converted to 5.54e-4 mm)
s= slit separation (1.5mm - provided by question)
w= width between maxima (use 5w do to question asking for 5 interference maxima)
D= distance to screen (90cm - converted to 900mm provided by question)

The Attempt at a Solution

Given that three of the four variables are known values, this should be simple as plug and solve. For some reason it is not liking the answer I am providing. The left side of the equation is simply 5.54e-4 / 1.5 which one would set equal to 5w / 900. Where am I going wrong here? Thanks in advance!

 

[msk172]

Follow up: Figured it out. Initially thought of the question as asking about 5 maxima per side (thus 10 total). One maxima in the center, two per side, 5 total. w * 4 yields correct value.