A lifeguard believed that the more swimmers were at the beach, the more seagulls showed up as well. He recorded the number of swimmers and number of seagulls that appeared each day for two weeks. He found that the variables were linearly related and the regression line equation was: y' = 1.8x + 30.4.

How many swimmers would you expect to be on the beach if there are 100 seagulls? Round to the nearest whole number (no decimals).

If the answer cannot be determined type 123456.