A European species of marsh grass called Spartina maritima has a diploid number

A European species of marsh grass called Spartina maritima has a diploid number (2n) of 60. A similar species native to North America, S. alterniflora, has 2n = 62. In 1835 the North American species was found growing near the European species in Southampton, England, after being accidentally imported. Occasional sterile hybrids were noted. In 1895 a new species, S. anglica, was first identified at Southampton and subsequently became very common. The new species has been identified as a fertile hybrid of the original two species. What is the 2n chromosome number of the hybrids that formed from the original two species S. maritima and S. alterniflora?
A) 31
B) 60
C) 61
D) 122
E) 153