Statistical Hypothesis Testing?

A school is concerned that dual degree students may be receiving lower grades than the regular students. Two independent random samples have been selected 250 observations from population 1 (dual degree students) and 210 from population 2 (regular students). The sample means obtained are X1(bar)=83 and X2(bar)=86. It is known from previous studies that the population variances are 4.6 and 5.0 respectively. Using a level of significance of .05, is there evidence that the dual degree students are receiving lower grades? Fully explain your answer.