Table:
text: List of Hewitts and Nuttalls in England
— Southern Fells
— Southern Fells
Peak Height_m Prom_m Class_ Parent
Whernside 736 408 Marilyn Cross Fell
Ingleborough 724 428 Marilyn Cross Fell
Great Whernside 704 288 Marilyn Whernside
Buckden Pike 702 207 Marilyn Great Whernside
Pen-y-ghent 694 306 Marilyn Whernside
Great Coum 687 221 Marilyn Whernside
Plover Hill 680 59 Hewitt Pen-y-ghent
Great Knoutberry Hill 672 254 Marilyn Great Whernside
Dodd Fell Hill 668 230 Marilyn Great Knoutberry Hill
Fountains Fell 668 243 Marilyn Pen-y-ghent
Fountains Fell south top 662 15 Nuttall Fountains Fell
Simon Fell 650 35 Hewitt Ingleborough
Yockenthwaite Moor 643 86 Hewitt Dodd Fell Hill
Green Hill 628 24 Nuttall Great Coum

text: List of Hewitts and Nuttalls in England
— Southern Fells
— Southern Fells
Peak Height_m Prom_m Class_ Parent
Gragareth 627 30 Hewitt Great Coum
Darnbrook Fell 624 40 Hewitt Fountains Fell
Drumaldrace 614 66 Hewitt Dodd Fell Hill
Birks Fell 610 158 Marilyn Pen-y-ghent

Question: Among the list Southern Fells of Hewitts and Nuttalls in England: What is the average height for the Hewitt class with a prom less than 86 and a peak of Gragareth?