Final answer:
Without additional information about another charge and the distance between charges, it is impossible to accurately calculate the force on qa given that qa=1.24nC.
Step-by-step explanation:
To determine the magnitude of the force on a charge qa, you would typically use Coulomb's Law, which states that the force (F) between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance (r) between them. The formula is F = k * |qa * qb| / r^2, where k is Coulomb's constant (8.9875 x 10^9 N*m^2/C^2). However, the question doesn't provide information about another charge (qb) or the distance between the charges, which are essential to calculate the force on qa. Without this additional information, it is impossible to calculate the force on qa, given solely that qa = 1.24 nC. More context or additional parts of the problem are required to provide a numerical answer.