Hello Sir, can you please mention the dimension for the Billboard?

Since this will be a road side digital billboard I was thinking of maybe changing the blue to more of a bold royal blue so it can be read clearly during daytime hours. I will post the dimensions and more comments on design soon. Also I like the size of the wording on the logo file that I posted more than the one on the website, where family dental care is the same length as alexandria.

Dimensons: 400h x 840w pixels @ 72ppi in RGB mode (21:10 aspect ratio)
they also said preferred color profile: sRGB