<image>There are a total of 300 eighth-grade students in a school. To understand the physical fitness of the students in this grade, a random sample of students was selected to undergo a 1-minute jump rope test. Four students, namely Jia, Yi, Bing, and Ding, were tasked with organizing the test result data. Below is the information provided by these four students:

- Jia: The entire test data is divided into 6 groups and displayed in a histogram (as shown in the figure).
- Yi: Students who jumped rope at least 105 times account for 96%.
- Bing: The sum of the frequencies of groups ① and ② is 0.12, with both groups ② and ⑥ having a frequency of 4.
- Ding: Group ③ has 2 more students than group ④, and the sum of the frequencies of groups ③ and ④ is four times the frequency of group ⑤.

Based on the information provided by these four students, please answer the following questions:  

 (1) How many students were sampled in this jump rope test? How many students are there in groups ① and ③, respectively?

 (2) If jumping rope at least 135 times is considered excellent, based on this sample, estimate the number of students in the entire grade who would achieve an excellent rating.