如何在R中的直方图图中设置特定的间隔?

我想绘制一个二进制宽度为4的直方图。我无法修正这些数据的间隔。我希望我的垃圾箱从x=28开始,从那时起间隔为4。例如28-32、32-36、36-40等等。我如何设置特定的间隔并固定直方图的开始值?

crushing_strength <- c(40,37.9,29,31.7,39.3,40.7,42.7,40,50.3,
                                  33.8,39.3,42.1,45.5,41.4,47.6,38.6,35.9,
                                  41.4,44.1,40,40.7,42.1,38.6,36.5,40.7)
test_no <- seq(1:25)

data_example <- data.frame(test_no,crushing_strength)


ggplot(data_example, aes(x = crushing_strength))+
  geom_histogram(binwidth=4)+
  scale_x_continuous()