How far from the base of the CN Tower should she stand?

Protestors unfurl a banner from the outdoor observation deck of the CN Tower, 342m above ground level. The banner is 20m long, and hangs vertically. To get the best picture, a news photographer 2m tall, standing at ground level, would like to stand where the banner appears largest. How far from the base of the CN Tower should she stand? Namely, what distance from the CN Tower maximizes the visual angle of the photographer?