Highest Sales in April

A company, ABC Corp, recorded the sales of three products (X, Y, and Z) over the first four months of the year. The following bar graph displays these sales figures in thousands of dollars:

Month:     January     February     March     April

Product X:     50     60     70     80

Product Y:     30     40     60     90

Product Z:     20     30     50     70

Based on the graph, which product had the highest sales in April?