A highway construction project includes a blasting zone. A sign reading “turn off two-way radios” must be posted in sequence with the blasting zone and blasting zone signs. These signs must be placed at least __ feet from the blasting zone.

A highway construction project includes a blasting zone. A sign reading “turn off two-way radios” must be posted in sequence with the blasting zone and blasting zone signs. These signs must be placed at least __ feet from the blasting zone.