要求：写一个Fortran90 fixed format程序，名字：student_info.F,包括内容如下：
建一个学生档案，学生的信息包括学号（整型），计算机成绩（实型），同时这些信息从屏幕（log in node）读入，读入后进行判断：如果成绩高于90分，输出“excellent”，如果是80-89，输出“Good”，如果是“60-79”，输出“Fair”，其余的输出“Fail”
我写的代码如下：
program assignment3
type :: person
integer :: schoolnumber
real :: score
character :: grade
end type person
type (person) :: a
character(len=12) b
character(len=10) c
character(len=10) d
character(len=10) e
b = "Excellent!"
c = "Good!"
d = "Fair!"
e = "Fail!"
write(*,*) "School number:"
read(*,*) a%schoolnumber
write(*,*) "Score:"
read(*,*) a%score
if (score >= 90) then
grade = "b"
else if (score >= 80) then
grade = "c"
else if (score >= 60) then
grade = "d"
else if (score >= 0) then
grade = "e"
else
grade = '?'
end if
write(*,"('Grade:',A10)") a%grade
write(*,100) a%schoolnumber,a%score,a%grade
100 format(/,"School number:",A10/,"Score:",A2/,"Grade:",A10)
end
请问如何修改呢？