A construction company has just completed a bridge over the Snake River. This is the first bridge the company ever built, and it required 100 weeks to complete. Now having hired a bridge construction crew with some experience, the company would like to continue building bridges. Because of the investment in heavy machinery needed continuously by this crew, the company believes it would have to bring the average construction time to less than one year (52 weeks) per bridge to earn a sufficient return on investment. The average construction time will follow an 80% learning curve. To bring the average construction time (over all bridges constructed) below one year per bridge, the crew would have to build approximately how many bridges?